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81.
G. A. Meehl R. Lukas G. N. Kiladis K. M. Weickmann A. J. Matthews M. Wheeler 《Climate Dynamics》2001,17(10):753-775
Interactions involving various time and space scales, both within the tropics and between the tropics and midlatitudes, are
ubiquitous in the climate system. We propose a conceptual framework for understanding such interactions whereby longer time
scales and larger space scales set the base state for processes on shorter time scales and smaller space scales, which in
turn have an influence back on the longer time scales and larger space scales in a continuum of process-related interactions.
Though not intended to be comprehensive, we do cite examples from the literature to provide evidence for the validity of this
framework. Decadal time scale base states of the coupled climate system set the context for the manifestation of interannual
time scales (El Nino/Southern Oscillation, ENSO and tropospheric biennial oscillation, TBO) which are influenced by and interact
with the annual cycle and seasonal time scales. Those base states in turn influence the large-scale coupled processes involved
with intraseasonal and submonthly time scales, tied to interactions within the tropics and extratropics, and tropical–midlatitude
teleconnections. All of these set the base state for processes on the synoptic and mesoscale and regional/local space scales.
Events at those relatively short time scales and small space scales may then affect the longer time scale and larger space
scale processes in turn, reaching back out to submonthly, intraseasonal, seasonal, annual, TBO, ENSO and decadal. Global coupled
models can capture some elements of the decadal, ENSO, TBO, annual and seasonal time scales with the associated global space
scales. However, coupled models are less successful at simulating phenomena at subseasonal and shorter time scales with hemispheric
and smaller space scales. In the context of the proposed conceptual framework, the synergistic interactions of the time and
space scales suggest that a high priority must be placed on improved simulations of all of the time and space scales in the
climate system. This is particularly important for the subseasonal time scales and hemispheric and smaller space scales, which
are not well simulated at present, to improve the prospects of successfully forecasting phenomena beyond the synoptic scales.
Received: 3 April 2000/ Accepted: 6 November 2000 相似文献
82.
Evaluating Topological Queries in Linked Data Using DBpedia and GeoNames in Switzerland and Scotland 下载免费PDF全文
This article explores the practicability and assesses the quality of searches for Wikipedia pages of topologically related administrative divisions in Switzerland and Scotland via Linked Data. To this end, the quality of searches in the English and German versions of DBpedia is compared, as is that of searches in GeoNames and DBpedia using DBpedia's links to GeoNames or a manually created list of links. In addition, the effects of updates to Swiss municipality borders in the English version of DBpedia on standard quality metrics are studied. It turns out that live searches are practicable with acceptable performance, but that the quality of searches in terms of recall and precision is acceptable only if DBpedia is queried via GeoNames and DBpedia's links to GeoNames are replaced by manually created links. Searches for Scottish unitary authority wards perform poorly for all approaches investigated. Recall and precision are strongly influenced by changes in municipality borders, with a relatively long latency suggesting that, at least in some cases, administrative changes propagate slowly into DBpedia. These results have important implications for those seeking to use location as a means to link data. 相似文献
83.
Katharopoulos Ioannis Brunner Dominik Emmenegger Lukas Leuenberger Markus Henne Stephan 《Boundary-Layer Meteorology》2022,185(1):129-160
Boundary-Layer Meteorology - Lagrangian particle dispersion models (LPDMs) are frequently used for regional-scale inversions of greenhouse gas emissions. However, the turbulence parameterizations... 相似文献
84.
Antoine S. G. Roth Knut Metzler Lukas P. Baumgartner Ingo Leya 《Meteoritics & planetary science》2016,51(7):1256-1267
If chondrules were exposed to cosmic rays prior to meteorite compaction, they should retain an excess of cosmogenic noble gases. Beyersdorf‐Kuis et al. (2015) showed that such excesses can be detected provided that the chemical composition of each individual chondrule is precisely known. However, their study was limited to a few samples as they had to be irradiated in a nuclear reactor for instrumental neutron activation analysis. We developed a novel analytical protocol that combines the measurements of He and Ne isotopic concentrations with a fast method to correct for differences in chemical composition using micro X‐ray computed tomography. Our main idea is to combine noble gas, nuclear track, and petrography data for numerous chondrules to understand the precompaction exposure history of the chondrite parent bodies. Here, we report our results for a total of 77 chondrules and four matrix samples from NWA 8276 (L3.00), NWA 8007 (L3.2), and Bjurböle (L/LL4). All chondrules from the same meteorite have within uncertainty identical 21Ne exposure ages, and all chondrules from Bjurböle have within uncertainty identical 3He exposure ages. However, most chondrules from NWA 8276 and a few from NWA 8007 show small but resolvable differences in 3He exposure age that we attribute to matrix contamination and/or gas loss. The finding that none of the chondrules has noble gas excesses is consistent with the uniform track density found for each meteorite. We conclude that the studied chondrules did not experience a precompaction exposure longer than a few Ma assuming present‐day flux of galactic cosmic rays. A majority of chondrules from L and LL chondrites thus rapidly accreted and/or was efficiently shielded from cosmic rays in the solar nebula. 相似文献
85.
Kathleen Schwerdtner Máñez Costa Maria Máñez Costa Martin Christian Lukas 《Ocean & Coastal Management》2009,52(3-4):229-232
With this paper we demonstrate, using the example of the Segara Anakan lagoon in south Java, Indonesia, that exploring the environmental history of an area may provide important information for the understanding of present day problems and their possible solutions. The lagoon is seriously affected by sedimentation. Management measures aiming at its preservation were rather ineffective. Until now, most scholars have treated sedimentation of the lagoon as a short-term phenomenon. We found evidence that sedimentation is a long-term driver of ecosystem changes in Segara Anakan. Ecosystem changes are also obvious in the disappearance of species from the lagoon, like pearl oysters.We recommend that preconditions for the development of adequate management decisions regarding the lagoon's sedimentation problem are (1) a distinction between natural and anthropogenic causes of sedimentation and (2) an understanding of changes in species composition. 相似文献
86.
Kathleen A. Donohue Mark Wimbush Xiaoli Zhu Stephen M. Chiswell Roger Lukas Laury Miller 《大气与海洋》2013,51(2):495-506
Abstract Temporal and spatial features of central equatorial Pacific Ocean sea‐level variation appear similar, in measurements from two very different systems (one in the ocean and one carried on a satellite), and in results from a numerical model of the region. In particular, there is an interannual cycle: during El Nino, Kelvin waves appear at the equator, and the sea‐surface ridge associated with the equatorial current system shifts southward; in non‐El Nino years, instability waves appear at 6°N (strongest around the end of each calendar year), and the ridge shifts to the north. This three‐way comparison gives support to both measurement systems and to the numerical model. 相似文献
87.
The export of organic matter from the oceanic euphotic zone is a critical process in the global biogeochemical cycling of bioelements (C, N, P, Si). Much of this export occurs in the form of sinking particles, which rain down into the unlit waters of the deep sea. Classical models of oceanic production and export balance this gravitational loss of particulate bioelements with an upward flux of dissolved nutrients, and they describe reasonably well those areas of the ocean where deep winter mixing occurs. The surface waters of the North Pacific Subtropical Gyre (NPSG), however, are strongly stratified and chronically nutrient-depleted, especially in summer. Nevertheless, there is ample evidence that blooms of phytoplankton and subsequent pulses of particle export occur during the height of summer stratification in these waters, especially to the northeast of the Hawaiian Islands. These blooms impact regional bioelemental cycling and act as a food source to the deep-sea benthos. We review here numerous published observations of these events in the NPSG, and present new data collected at Station ALOHA (22.75°N, 158°W) during the first 176 cruises of the Hawaii Ocean Time-series program (1988-2005), along with results from transect cruises conducted in the region in 1996 and 2005. We suggest that the summer phytoplankton bloom can be considered a frequent, perhaps annual feature in the northeastern NPSG, and that its perceived stochastic nature is a manifestation of chronic undersampling in time and space. The bloom is typically dominated by only a few genera of large diatoms and the cyanobacterium Trichodesmium. It appears to be consistently supported by dinitrogen fixation, but the fate of the organic matter produced during the summer depends critically on the species composition of the responsible diazotrophs. We estimate that the summer bloom is responsible for up to 38% of N2 fixation and up to 18% of N-based new production annually at Station ALOHA. We hypothesize that the spatial distribution, timing and magnitude of the bloom may be determined largely by the physical and biological processes controlling new phosphorus delivery into the euphotic zone during the summer and the preceding winter. 相似文献
88.
Acta Geochimica - Asian dust has been identified in subtropical soils of China. Neodymium (Nd) and lead (Pb) elemental and isotopic geochemistry of soils in Southeast China were used to assess the... 相似文献
89.
90.
Johannes Schmidt Lukas Werther Johannes Rabiger-Völlmer Franz Herzig Birgit Schneider Ulrike Werban Peter Dietrich Stefanie Berg Sven Linzen Peter Ettel Christoph Zielhofer 《地球表面变化过程与地形》2020,45(14):3449-3462
Sediment budgeting concepts serve as quantification tools to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment-based studies, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The Fossa Carolina is one of the largest hydro-engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876°N, 10.9267°E; Bavaria, southern Germany) between the Altmühl and Swabian Rezat rivers. It should have bridged the Central European watershed and connected the Rhine–Main and Danube river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short-term erosion event has been proposed as the principal reason for the collapse and abandonment of the hydro-engineering project. We use subsurface data (drillings, archaeological excavations, and direct-push sensing) and geospatial data (a LiDAR digital terrain model (DTM), a pre-modern DTM, and a 3D model of the Fossa Carolina] for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro remains within the backfills give clear evidence for the erosional collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献